My av300 s (have 2 of them) charge fine with a 2amp 5 v charger from Radio Shack But won't charge through a power bank (5 v 2.1amp 8000 mh rated) or a battery pack from New Mp3 Tech that takes 4aa cells or a car charger using a USB to dc plug. Anyone know anything about this? All I can come up with is that the charging circuit needs at least 2 or more amps to work. The voltages on all these chargers are at least 5 to 5.25v

That is strange. I remember using a car charger set to 4.5V for the MMJB and Av300 which worked, and the Av300 worked on other 5V chargers then the supplied Archos ones. I also used the 4AA pack with NiMH rechargeables which are only nominally 4.8V when fully charged to increase playing time.

The only thing I can think of is the internal impedance output of the supplies that don't work may be higher than the regulator circuit of the Av300 likes? - if there is no fault anywhere, which doesn't seem to be the case if they charge normally on some supplies. The internal circuit of switching regulators can vary, especially very cheap ones from China.